1. Field of the Invention
The invention relates to a process for post reactive ion etching (RIE) polymer removal on an organic low K dielectric through the use of reducing plasma chemistry. The process removes extensive post RIE polymer on an organic low K dielectric material by use of a reducing gas plasma and comprises either a forming gas mixture of (N2/H2) or an ammonia/hydrogen (NH3/H2) mixture to completely remove the post reactive ion etch by-product from a wafer surface or a Via structure prior to a wet chemical clean. The removal is achieved without significant removal of the organic, low K dielectric material that is exposed to the gas plasma.
2. Description of the Related Art
Existing post RIE plasma clean solutions use oxidizing chemistries; however, these chemistries cannot be utilized with organic low constant (K) dielectrics due to the extremely poor selectivity of the polymer strip/clean to the organic low K dielectric material.
In particular, a case in point is the accomplishment of post RIE polymer cleaning by utilizing a chromic-phosphoric acid tank bath or other solvent based chemistry. In this process, there is a certain time window of approximately 4 hours between completion of the RIE process and the wet cleaning step.
However, some drawbacks of currently existing wet chemical cleaning methods are as follows: an acid based chemistry (without any HF in it) is not efficient in removing polymer that have high silicon content (as found in metal pads located in the support region); and a solvent based chemistry generally takes a longer process time (approximately 10 minutes as compared to 2 to 4 minutes for a typical acid based clean) and typically is encumbered as a result of costs and environmental disposal requirements.
U.S. Pat. No. 5,780,359 disclose polymer removal from top surfaces and sidewalls of a semiconductor wafer by: initiating a flow of feed gas comprising fluorine-containing gases upstream from the process chamber; applying the feed gas means for producing a plasma; supplying effluents of the plasma in the form of reactive species separated from the plasma to the process chamber; applying radio frequency energy to the wafer in the process chamber to generate a lower intensity plasma therein and accompanying wafer self-biasing; applying a magnetic field that rotates slowly in the horizontal plane to the process chamber during the step of applying radio frequency energy to the wafer to enhance plasma generation; and stripping the photoresist and polymer residues from the top surfaces and sidewalls of the post metal-etch wafer with the reactive species and the lower intensity plasma; wherein the pressure in the process chamber is greater than 100 milliTorr
A process for removal of post-RIE polymer on Al/Cu metal line is disclosed in U.S. Pat. No. 5,980,770. The process entails: supplying a mixture of an etching gas and an acid neutralizing gas into a vacuum chamber in which the composite structure is supported to form a water soluble material of sidewall polymer rails left behind on the Al/Cu metal line from the RIE process; removing the water soluble material with deionized water; and removing photo-resist from the composite structure by either a water-only plasma process of the chemical down stream etching method; or forming a water-only plasma process to strip the photoresist layer of a semiconductor or microelectronic composite structure previously subjected to a RIE process; supplying a mixture of an etching gas and an acid neutralizing gas into a vacuum chamber on which the structure is supported to form a water soluble material of the sidewall polymer rails left behind on the Al/Cu metal line from the RIE process; and removing the water-soluble material with deionized water.
U.S. Pat. No. 6,009,888 disclose a method of stripping photoresist and polymer from a wafer after a dry etch, comprising: forming a photoresist pattern over a semiconductor structure; immersing the substrate in a bath comprising (a) peroxydisulfate (S2O82xe2x88x92) (bisulfate), (2) hydrochloric acid (HCl) and (3) water; and agitating the semiconductor structure in the solution; said bath being at a temperature in a range of between about 90 and 100xc2x0 C.; irradiating the semiconductor structure, and the photoresist pattern with a UV laser with a wave length between about 150 nm and 300 nm, and with an energy between about 4 and 8.0 eV and laser pulses in a range of between about 10 and 10,000 per wafer to remove the photoresist.
Previous approaches for removing RIE polymer from semiconductor materials used no post RIE clean, and this led to high contact resistance and reliability failures.
Alternatively, when previous approaches utilized wet chemical only clean, this caused severe contamination of the wet chemical bath from delaminating fluoropolymer on the wafer surface deposited during RIE processes.
There is a need in the art of cleaning RIE etched materials to remove fluoropolymer/hydrocarbon from the surface of an organic low k dielectric material without excessive removal of organic dielectric material.
One object of the present invention is to provide a process to completely remove post-reactive ion etch (RIE) by-product from a wafer surface or Via structure prior to wet chemical clean.
Another object of the present invention is to provide a process for removing post-reactive ion etch (RIE) by-product from a wafer surface or Via structure prior to a wet chemical clean by utilizing a reducing gas plasma incorporating a forming gas mixture of N2/H2.
A further object of the present invention is to provide a process to completely remove post-reactive ion etch (RIE) by-product from a wafer surface or Via structure prior to a wet chemical clean by utilizing a reducing gas plasma incorporating a forming gas mixture of NH3/H2.
A still further object of the present invention is to provide a process for completely removing post-reactive ion etch (RIE) by-product from a wafer surface or Via structure prior to a wet chemical clean without significant removal of an organic, low dielectric constant material which is exposed to either a reducing gas plasma incorporating either a forming gas mixture of N2/H2 or NH3/H2.
A yet further object of the present invention is to provide a process for completely removing post-reactive ion etch (RIE) fluoropolymer strip from either single or dual damascene structures by utilizing a reducing gas plasma incorporating either a forming gas mixture of N2/H2 or NH3/H2.